From owner-svn-src-head@FreeBSD.ORG  Sun Nov  7 18:42:38 2010
Return-Path: <owner-svn-src-head@FreeBSD.ORG>
Delivered-To: svn-src-head@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 62A151065672;
	Sun,  7 Nov 2010 18:42:38 +0000 (UTC) (envelope-from alc@FreeBSD.org)
Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:4f8:fff6::2c])
	by mx1.freebsd.org (Postfix) with ESMTP id 5140D8FC15;
	Sun,  7 Nov 2010 18:42:38 +0000 (UTC)
Received: from svn.freebsd.org (localhost [127.0.0.1])
	by svn.freebsd.org (8.14.3/8.14.3) with ESMTP id oA7IgboR070624;
	Sun, 7 Nov 2010 18:42:37 GMT (envelope-from alc@svn.freebsd.org)
Received: (from alc@localhost)
	by svn.freebsd.org (8.14.3/8.14.3/Submit) id oA7Igb8Y070622;
	Sun, 7 Nov 2010 18:42:37 GMT (envelope-from alc@svn.freebsd.org)
Message-Id: <201011071842.oA7Igb8Y070622@svn.freebsd.org>
From: Alan Cox <alc@FreeBSD.org>
Date: Sun, 7 Nov 2010 18:42:37 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
	svn-src-head@freebsd.org
X-SVN-Group: head
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Cc: 
Subject: svn commit: r214938 - head/sys/i386/i386
X-BeenThere: svn-src-head@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: SVN commit messages for the src tree for head/-current
	<svn-src-head.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
	<mailto:svn-src-head-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-head>
List-Post: <mailto:svn-src-head@freebsd.org>
List-Help: <mailto:svn-src-head-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
	<mailto:svn-src-head-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 07 Nov 2010 18:42:38 -0000

Author: alc
Date: Sun Nov  7 18:42:37 2010
New Revision: 214938
URL: http://svn.freebsd.org/changeset/base/214938

Log:
  Eliminate a possible race between pmap_pinit() and pmap_kenter_pde() on
  superpage promotion or demotion.
  
  Micro-optimize pmap_kenter_pde().
  
  Reviewed by:	kib, jhb (an earlier version)
  MFC after:	1 week

Modified:
  head/sys/i386/i386/pmap.c

Modified: head/sys/i386/i386/pmap.c
==============================================================================
--- head/sys/i386/i386/pmap.c	Sun Nov  7 18:25:42 2010	(r214937)
+++ head/sys/i386/i386/pmap.c	Sun Nov  7 18:42:37 2010	(r214938)
@@ -1678,11 +1678,19 @@ pmap_unuse_pt(pmap_t pmap, vm_offset_t v
 	return (pmap_unwire_pte_hold(pmap, mpte, free));
 }
 
+/*
+ * Initialize the pmap for the swapper process.
+ */
 void
 pmap_pinit0(pmap_t pmap)
 {
 
 	PMAP_LOCK_INIT(pmap);
+	/*
+	 * Since the page table directory is shared with the kernel pmap,
+	 * which is already included in the list "allpmaps", this pmap does
+	 * not need to be inserted into that list.
+	 */
 	pmap->pm_pdir = (pd_entry_t *)(KERNBASE + (vm_offset_t)IdlePTD);
 #ifdef PAE
 	pmap->pm_pdpt = (pdpt_entry_t *)(KERNBASE + (vm_offset_t)IdlePDPT);
@@ -1692,9 +1700,6 @@ pmap_pinit0(pmap_t pmap)
 	PCPU_SET(curpmap, pmap);
 	TAILQ_INIT(&pmap->pm_pvchunk);
 	bzero(&pmap->pm_stats, sizeof pmap->pm_stats);
-	mtx_lock_spin(&allpmaps_lock);
-	LIST_INSERT_HEAD(&allpmaps, pmap, pm_list);
-	mtx_unlock_spin(&allpmaps_lock);
 }
 
 /*
@@ -1759,9 +1764,9 @@ pmap_pinit(pmap_t pmap)
 
 	mtx_lock_spin(&allpmaps_lock);
 	LIST_INSERT_HEAD(&allpmaps, pmap, pm_list);
-	mtx_unlock_spin(&allpmaps_lock);
-	/* Wire in kernel global address entries. */
+	/* Copy the kernel page table directory entries. */
 	bcopy(PTD + KPTDI, pmap->pm_pdir + KPTDI, nkpt * sizeof(pd_entry_t));
+	mtx_unlock_spin(&allpmaps_lock);
 
 	/* install self-referential address mapping entry(s) */
 	for (i = 0; i < NPGPTD; i++) {